1. Field of the Invention
The invention relates in general to a scanning device, and more particularly to a scanning device with two scanning modes and the carriers used in the scanning device have different thicknesses or refractive indexes.
2. Description of the Related Art
Nowadays, the scanning device has been widely used in a wide range of office equipment such as scanners, copiers, and multi-functional machines. Along with the advance technology, the scanning device with dual-scanning modes is also provided. One of the two modes is a static scanning mode, which scans the original document placed on the glass carrier by moving the imaging module. The other mode is a dynamic scanning mode, which uses the imaging module, being static, to scan the original document moved in different regions of the same or a different glass carrier by a device such as an automatic document feeder (ADF).
There imaging module has two types, namely, the charge coupling device (CCD) scanning module and the contact image sensor (CIS) scanning module. The CCD module has a larger depth, so the two glass carriers corresponding to the two scanning modes can be designed to be stacked or parallel in the scanning device. However, the CCD module is disadvantaged by having a huge volume and cannot meet the requirement of miniaturization. To the contrary, the CIS module, being small in size and compact in structure, meets the requirement of miniaturization. However, due to the shallow depth, the glass carrier of the CIS module corresponding to the two scanning modes cannot be designed as a stacked structure.
Referring to FIG. 1A and FIG. 1B. FIG. 1A and FIG. 1B respectively show the scanning device 1 according to prior art. The scanning device 1 includes a CIS module 10, a first carrier 11, a second carrier 12 and a holder 13. The CIS module 10 is for reading the image of an original document. The first carrier 11 is for carrying the original document in a dynamic scanning mode. The second carrier 12 is for carrying the original document in a static scanning mode. The holder 13, used for fixing the first carrier 11 and the second carrier 12, includes a transitional portion 131 disposed between the first carrier 11 and the second carrier 12. The first carrier 11 and the second carrier 12 are disposed in the scanning device 1 in parallel. Since the two glass carriers have the same thickness and the glass has the same refractive index, when the CIS module 10 is moved between the underneath of the first carrier 11 and the underneath of the second carrier 12, the design requirement of the CIS module's depth will be satisfied as long as the distance between the CIS module 10 and the bottom surface of the carrier remains the same. Despite such structural design is simple, the first carrier 11 and the holder 13 are hard to be fixed. As indicated in FIG. 1B, firstly, to assure paper jam will not occur to the original document, the corner above the carrier must have a positive flushness in the feeding direction Z of the original document. Next, due to the structure of the CIS module 10 and the design of crossing over the transitional portion 131, the transitional portion 131 of the holder 13 cannot be extended towards the underneath of the first carrier 11 to support the first carrier 11. One of the currently used methods is to fix the first carrier 11 with glue. However, such method is troublesome and is inconvenient for the assembly of the product. Moreover, since the gap between the first carrier 11 and the holder 13 is interconnected to the inside of the scanning device 1, the dust may easily enter the scanning device through the gap so as to deteriorate the quality of image scanning.